A hard disc drive, one of the magnetic storage devices in a computer, shows remarkable technical advances in achieving high-speed, high density, mass storage and the like. Its magnetic head for reading/writing is required to read/write on the surface of a magnetic disc rotating at a high speed, without a contact therewith but maintaining a small gap of a submicron order.
There can be mentioned a suspension board with a circuit, as a component for elastically pushing a magnetic head toward a magnetic disc surface rotating at a high speed, while resisting the airflow generated in the small gap, thereby to maintain a small gap between a surface of the magnetic disc and the magnetic head.
In a suspension board with a circuit, an elastic metal such as a stainless steel foil and the like is used as a material of the board, wherein one embodiment of the shape of the whole parts is, as shown in FIG. 1 of JP-A-10-12983, a kind of a band-like flat spring having a magnetic head mounting area and a circuit pattern.
A base end side of a suspension board with a circuit is fixed to an arm member extending from a device body of a hard disk driver and a magnetic head is mounted on a tip side (free end side), and the suspension board has a configuration wherein the board elastically supports the magnetic head on the tip side like a cantilever.
FIG. 8 is a schematic view of an enlarged tip part alone of a conventional suspension board with a circuit, and shows the configuration of the circuit and connections. A protective film covering the circuit, and so on have been omitted.
As shown in FIG. 8, the tip part of a metal board 100 has an area 130 to mount a magnetic head thereon, and a through-hole 140 is formed to surround therearound, whereby the area 130 is supported like a cantilever on the tip side alone at the center of the tip part of the metal board 100.
Furthermore, a conductive layer (circuit pattern shown with exta-thick line) 120 to transmit power, signal and the like is formed from the base side (not shown) of the board to the terminal of the magnetic head on the metal board, via an insulation layer 110. Said circuit pattern 120 has a pattern end 121 to be a connection terminal (or terminal pad, electrode pad) is formed to connect a terminal of the magnetic head.
While various bonding methods have been proposed to connect the terminal of a magnetic head and an end of a pattern, techniques to connect them using a solder has been adopted in recent years so that even if the attached magnetic head is defective, only the magnetic head can be replaced easily without discarding the whole assembly.
Particularly, as a method for dealing with small terminals of magnetic heads and narrow-pitched arrangement thereof, connecting methods using a solder ball can be mentioned. As shown in FIG. 9(a), this connecting method comprises first arranging a terminal H11 of a magnetic head H10 and a pattern end (terminal pad for connection) 121 of a circuit closely to each other forming a right angle, and supplying a solder ball 150 in contact with both terminal surfaces. Then, a laser beam is irradiated on the ball to melt it as shown in FIG. 9(b) with a reference number 151 to establish a connection.
JP-A-10-79105 and JP-A-2002-50018 describe in detail connection methods using a solder ball, a supply device (solder ball supply element) of a solder ball and the like.
However, the present inventors have examined in detail conventional connection methods using a solder ball and found that the positioning of laser beam irradiation and the positioning of solder ball need to be improved.
To be specific, according to the observation by the present inventors, when a magnetic head is made to be smaller and both connection terminals and a solder ball are made to be smaller, accurate irradiation of a laser beam solely on a solder ball (positioning of laser beam irradiation) becomes difficult, and as shown in FIG. 10, the vicinity of the outer circumference of a pattern end 120 and the like are often exposed to the beam. At the outer circumference of the pattern end 120, since, as shown in FIG. 10 by m, a lower insulation layer 110 extends from the pattern end, the extended part m is also exposed to the laser beam.
The insulation layer exposed to the laser beam is thermally decomposed and thermal decomposition products such as carbon and the like are produced. These thermal decomposition products adversely affect driving of the magnetic head, and may cause functional problems such as inhibition of electric signal and the like.
Furthermore, it has been found that, due to the dispersion in the positions of the solder balls 150 disposed on the pattern end 120, besides the problem of positioning of laser beam irradiation, the laser beam may be irradiated onto the insulation layer rather than the solder ball.
It is therefore an object of the present invention to solve the above-mentioned problems and provide a suspension board with a circuit, which has a structure wherein a laser beam is not easily irradiated on an insulation layer even if the beam is irradiated around a solder ball, and furthermore, dispersion in the placing positions of solder balls can be minimized.